| Agricultural multi-axis UAVs are different from other kinds of aircraft.They need to fly close to the plant in the process of operation.Ultra-low altitude flight requires rapid flight attitude adjustment.In the dynamic process,it is one of the key problems in the design of flight control system for agricultural unmanned aerial vehicle to make the adjustment time as short as possible and the overshoot small.In this paper,the control algorithm is studied to improve the dynamic control effect of the aircraft.In this paper,a small four-rotor UAV test prototype is built.According to its flight principle,the dynamic model of the four-rotor UAV is established and its related physical parameters are measured.The transfer function of the attitude angle of the four-rotor UAV is obtained.Based on the traditional cascade integer-order PID,a cascade fractional-order PID is proposed,in which the inner loop is fractional-order PID and the outer loop is integer-order PID.Because of the difficulty of parameter tuning,the parameters of the two control algorithms are tuned by using the genetic algorithm toolbox of Matlab.The simulation model of roll angle is built by matlab,and the control effect of the two control algorithms is compared.The simulation results show that the two control algorithms have no overshoot.The cascade fractional-order PID is 31.9% shorter than the traditional cascade integer-order PID in adjustment time,and the cascade fractional-order PID control effect is better.According to the quality change characteristics of agricultural multi-axis UAV during operation,a cascade fuzzy fractional-order PID with inner ring as fractional-order PID and outer ring as fuzzy integer-order PID is proposed.The simulation results show that the cascade fuzzy fractional-order PID has better control effect when the quality changes.The actual test is carried out on the test prototype of Four-rotor UAV.The test results show that the cascade fractional-order PID control has better control effect,shorter adjustment time,shorter 0.24 s than cascade integer-order PID control,and better follow-up performance than cascade integer-order PID control.In order to realize the autonomous cruising operation of agricultural UAV,based on solving the attitude control problem,aiming at the navigation accuracy problem of agricultural UAV,this paper combines the characteristics of RTK and inertial navigation system,which have high positioning accuracy but are susceptible to interference or even loss of signals,puts forward the integrated navigation system which combines the two,and realizes different information processing methods according to the different positioning output.The experimental results show that the scheme has certain feasibility. |
