Research On Spraying Characteristics And Control System Of Variable-Rate Spraying Device

Variable-rate spraying technology is an important component of precision agriculture technologies. It is widely used in planting, livestock, horticulture and forestry. Developed countries pay a lot of attention and huge investment for the research on variable-rate implementing machines. They have developed mature variable-rate spraying system based on maps or real time sensing technology. During recent years, our government has increased the fiscal support to agriculture and paid more and more attention on variable-rate spraying technology.The core of variable-rate spraying technology is to get the differences of plant diseases in small farmland areas, take effeicient spraying technology and variable-rate spraying technology to spray according to the need. This paper analyses and summarizes domestic and foreign articles about variable-rate spraying technology. This paper develops a set of control system for variable-rate spraying and dynamic data acquisition, builds the test bench to study the spraying control characteristics of variable-rate system. Its main contents are as follows:(1) The boom sprayer structure is improved into the spraying device with variable-rate spraying function, and its spraying control system is designed; the variable-rate spraying control loop schemes are analyzed and compared and finally the bypass throttle modulating control circuit is adopted; the components of the variable-rate spraying control loop are designed and selected.(2) In order to study the spraying characteristics of spraying device, the effect of boom motion on the spraying deposit and the effect of ground excitations on boom motions are analyzed, the sprayer boom and suspention model of variable-rate sprayer is established, the dynamics of wide sprayer boom under different excitations is analyzed and simulated, and the effects of different boom motions on spraying deposit are analyzed.(3) According to the scheme of variable-rate spraying control system, this paper analyzes and establishes the variable-rate spraying control hardware system and software system, uses the master-slave mode based on bus communication to realize the real-time signal acquisition and intelligen control. The circuit design, development and dubugging of slave computer are completed; the executable program for the control of variable-rate spraying is developed by Visual Basic software; finally the comprehensive debugging of program is finished.(4) According to the flow regulating requirements, a fuzzy PID flow control algorithm of variable-rate system is studied. Considering the nonlinearity and high delay of TEEJET 346BR-2 electric regulating ball valve, the fuzzy PID control algorithm is adapted to achiece the flow adjustment. The simulation results show that the altorithm has certain superiority in flow control.(5) The throttle characteristics and the effect of adaptive fuzzy PID control of variable-rate spraying control system is analyzed and tested by experiments. The flow characteristics of throttle valve are tested and the relationship curve between the throttle valve opening degree and the amount of spray is getted; the flow response characteristics under fuzzy PID control is tested and the results show that this control algorithm can meet the control requirements of variable-rate spraying system.The research work of this thesis is to develop s set of variable-rate spraying control system which suits the present farmland management conditions in our country and could realize variable-rate spraying, real-tiem data acquisition and control. It provides technical support for sprayer promotion and realization.