| In view of the unreasonable spraying of drugs and low operating efficiency in the traditional crop plant protection mode,in recent years,with the rapid development of drone technology and micro-control technology,plant protection operations with drones have gradually been favored by agricultural producers.The existing application techniques mainly focus on adjusting the atomization effect of the nozzle and changing the water-drug ratio.For rural areas with large areas and complex environments,there are often disadvantages such as high implementation cost and low efficiency.Based on the real-time control of the application rate of plant protection drones as a variable,a variable application system based on the control speed of plant protection drones was analyzed and studied.The UAV speed signal outputted by the flight controller in real time is processed by an external MCU to form a PWM(Pulse Width Modulation)signal,and then the signal is applied to the flow control system to realize the time-varying application of the UAV speed.Volume control research.The main research contents of this paper are as follows:1.Analyze and determine the overall system design of the study.According to the system design purpose and requirements,the high stability UAV control scheme and the high control precision flow control scheme which are commonly used in the current plant protection operation are analyzed and expounded respectively.After analysis and comparison,the UAV flight platform system under the open source architecture of the flight controller is selected,and the flow control system with the MCU as the controller is selected.The flow control system is controlled in real time by means of PWM technology.2.System hardware design selection.Select APM2.8 open source flight controller and Tianyi model T900 to form the plant protection six-rotor UAV subsystem,select Arduino UNO microcontroller,micro DC motor,motor drive module and other flow control subsystems,select wireless receiver,digital transmission module and notebook The computer forms the ground station system and analyzes the main functional modules of each subsystem.3.System model establishment and control algorithm design.Based on the theory of aircraft dynamics,Newton classical mechanics,combined with UAV platform,the mathematical model of UAV attitude control is established and the PID optimal attitude control algorithm of double closed-loop series-pre filter is proposed.The flow control strategy is analyzed and utilized.The theory of automatic control,single-chip control,etc.,establishes the mathematical logic model of UAV flight speed and DC motor speed,and designs the incremental control algorithm with time-varying PWM signal as input with MCU as the control core.4.Software design.With the operating environment Arduino IDE,using the serial debugging assistant OpenJumper-Serial-Assistant-1.3.6,the serial communication between the plant protection UAV flight controller output parameter and the flow control system master is established.Real-time control of the flow control system unit through the main controller MCU software program.5.System algorithm simulation experiment.The simulation tool MATLAB is used to simulate the attitude control algorithm of the plant protection six-rotor UAV and the single-chip flow control algorithm based on time-varying PWM signal.The results show that the steady state error of the attitude control algorithm is 0,the steady state adjustment time of the system is ts<1s,and the system overshoot is less than 5%,which satisfies the system’s rapidity and stability requirements for dynamic performance indicators.Under the duty cycle signal,the system control time and stability of the flow control algorithm are ideal.Under different duty cycle signals,the motor speed control error of the flow control system is less than 5%,and the control effect meets the expected requirements.The control scheme of controlling the application rate of plant protection drone flight speed can achieve theoretical control demand and precision. |
