Design And Algorithm Research Of The Auto Variable Spraying System Based On ARM7

As the development of the technique of information, GPS and intelligent control, an innovation of precision agriculture was proposed, of which the main idea is the location management to the crop, and the variable devotion due to the practical needs. Its actual meaning is that, according to the practice of the crop, the management of the soil and crop should be better adjusted, and the agriculture devotion should be greatly optimized, so the great economic efficiency, the better zoology environment, and the protection of the agriculture resource can be realized. The conduction of precision agriculture can not only promote the productivity, but also is an effective way to realize the maintainable developing agriculture with high quality, high productivity, low cost and environment protection.As other fertilizers needed in agriculture, insecticide is the one which cannot be absent during the growing of the crops. So how to use insecticide reasonably and properly has become a key problem of promoting high quality and high productivity of agriculture productions, which make variable spraying be a research field in the precision agriculture. Based on the above trend, an auto-variable spraying system based on S3C44B0 is designed by this paper. The working process of the system is as follows. The information, which involves the location and speed of the spraying machine, is received by the GPS receiver from the satellite station, then it is transferred to the ARM7 controller through UART. The location information is processed, due to which the spraying information is obtained from the database which is made by the agriculture experts beforehand. Furthermore, the reasonable signals are sent to the solenoid on/off valve, electric valve, liquid pump combined with the storage information of spraying, spraying machine speed, the flow sensor, pressure sensor and the control algorithm, which make the practical spaying quantity be agree with that of the database. Then the normal function of variable spraying is realized. The main task and conclusions of this paper are as follows:(1) Aspects of hardware:This system takes S3C44B0-ARM7TDMI as the core control device, touch-screen LCD, keyboard and PS2 mouse as the human interface (by which input the data information and control information), solenoid on/off valve, electric valve, liquid pump as the driving devices, EEPROM as the storage device, and also takes the turbine flow sensor and resistor strain gauge sensor as the flow sensor and pressure sensor, respectively. The circuits of above modules were designed and described. To realize the reuse of the system, the core controller board and the main control board are designed apart, and the two boards are connected by an insert slot, which makes it more convenient and efficient for the upgrade of the system especially when changing the main control board, which is due to the reuse of the core board. Moreover, to provide the powers to the system by using the +12V voltage from the spraying machine, the circuits of reverting voltage and regulating voltage are designed, which first obtain a 220V alternating voltage from the +12V DC voltage, then the +5V, +3.3V, and±12V are obtained through the regulating voltage modules.(2) Aspects of software:The main functions of the software of the designed system are as follows: reading and processing of the spraying machine's location and moving speed; that of the keyboard; that of the sensors; that of the PS2 mouse; control of the system pressure and liquid flow; storing and reading of the spring database and displaying of the LCD. The detailed software flows of above function modules are designed, the programs are compiled based on the Embest IDE complier, and the correction and reasonability are checked by the ARM7 experimental board.(3) Aspects of algorithm:As the core chapter of this paper, the main contents are given as follows. Firstly, the mathematic models of the flow sensor, pressure sensor, transformer, solenoid on/off valve and electric valve are presented, of which the relations between input and output variables are discussed, and this is a basis for the foundation of the control algorithm and model; the control schematics of the location information and grid axis, the close loop control models of the pressure and flow are described, of which the transfer function and formulas are given; the control principle and method of the designed system are described, the control flow of the pressure, liquid flow and main algorithm are detailed analyzed; a new control method consists of the fuzz control method and model control method is proposed, which makes the spraying control more precisely and briefly; the mathematic models of the pressure and flow are simulated. The effects on the spraying caused by the integral time coefficient and the delay coefficient are discussed, and relation between such effects and the spraying machine speed is analyzed.(4) Data processing:Some methods of data processing are discussed, possible error sources of control system are analyzed and the ways of implementing are given. This can be useful and helpful to our experiment and practical use.As a conclusion, the main tasks and some novelties of this thesis are as follows:(1) From the view of process control, the mathematic models of the flow sensor, pressure sensor, transformation device, solenoid on/off valve and electric valve are described, the relations of whose input and output are discussed. This provides a foundation to establish the algorithm model and to analyze the algorithm itself.(2) The control principle and method of the designed system are described, the control flow of the pressure, liquid flow and main algorithm are detailed analyzed. A new control method consists of the fuzz control method and model control method is proposed, which makes the spraying control more precisely and briefly.(3) The mathematic models of the pressure and flow are simulated. The effects on the spraying caused by the integral time coefficient and the delay coefficient are discussed, and relation between such effect and the machine speed is analyzed.(4) The hardware drive program of the PS2 mouse is compiled, which makes the operation more conveniently. Some interfaces related to embedded system are designed and reserved, which provide the convenience of extend the designed system to the stage based on an embedded control system.In the end, some problems and their improving methods of this system are described here.(1) Because of the complicated reading and management and limit storage size of EEPROM, some novel devices of spraying information's storage should be used, such as SD card, CF card and U memory.(2) Considering the design cycle and cost, the embedded system is not used in the design, which may cause effects to the usage and management of PS2 mouse, SD card, CF card and U memory.(3) Due to the progress of the system, the experiment of our control algorithm and model are not carried out. So our next job is to check and change our designed spraying control algorithm.(4) Because the total power assumption of the system are not taken into account, which may affect the practical experiment, the proper reverting voltage device with suitable power should be better selected in the coming experiment.