Design And Implementation Of Four-rotor UAV Control System

In recent years,UAV has achieved extensive attention both at home and abroad because of its outstanding maneuverability,motility,and relatively low manufacturing costs.As a under-actuated nonlinear system,UAV is a complicated system.Also,during landing process,UAV easily deviates from its original planned landing site because of the inaccurate GPS.In this paper,a UAV control system was designed,and the control algorithm and anti-wind disturbance were studied.The main contents are as follows:(1)For the design of the control system of UAV,firstly,the mathematical model of UAV was established by coordinate transformation and Newton-Euler formula.In order to research motion of UAV under the wind disturbance,the wind disturbance environment such as mean wind,gust and turbulence wind field was modeled.(2)According to the mathematical model of UAV,the fuzzy PID control algorithm and sliding mode control algorithm were studied respectively.By adjusting the membership function of fuzzy PID control and also ameliorating chattering phenomenon in sliding mode control,improved the dynamic characteristic of UAV.Fuzzy PID control and sliding mode control were compared and it turned out that fuzzy PID control had better dynamic characteristic while sliding-mode control had stronger ability to resist wind.(3)Aiming at the color ring target plate,the paper designed image recognition method for automatic landing.Firstly,the method discussed the color space,pinhole projection model and camera distortion model and acquired camera’s intrinsic parameters through calibration process.Then,the paper studied Canny-operator edge-detection algorithm and Hough circle transformation in order to recognize circular contour and locate its center.(4)The software and hardware platforms were analyzed,and the fixed height module for indoor flight and the image recognition module for high precision landing were designed in this paper.(5)Finally,the paper debugged the hardware and software,designed indoor and outdoor flight experiments.In the indoor experiment,UAV had good hovering performance under the interference of mean wind and gust.In outdoor experiment,UAV was stable in the fifth level wind field of flight.The results showed that the designed control algorithm can meet the requirement.