Design Of Small Tilt-rotor UAV And Research On Flight Control

The tilt-rotor unmanned aerial vehicle（UAV）combines the vertical take-off and landing capabilities of a multi-rotorcraft with the efficiency of a fixed-wing aircraft,so it has promising application prospects.However,the composite structure of tilt-rotor aircraft introduces serious and complex coupling problems.On the one hand,the redundant manipulation structure increased energy consumption and reduced fight efficiency.On the other hand,the coupled flight dynamics caused great difficulties to the flight controls.This paper mainly studies the flight efficiency and control stability of tilt-rotor aircraft from the aspects of structural design,manipulation strategy,fight control algorithm and so on.Firstly,the overall layout of the tilt-rotor aircraft is proposed,in which the rotor and the fixed wing are separated.Aircraft components such as wings,rotor systems and tilting mechanisms are also designed.CFD technology was used for numerical simulation to analyze the aerodynamic performance of the wing,and the lift coefficient and the drag coefficient were calculated as 0.9310 and 0.05524,respectively.By collecting the data of the rotor thrust versus the rotor rotational speed,the fitting calculation shows that the thrust coefficient is 3.049×10^-5N/ω2.Secondly,the multi-body modeling method is used to analyze the dynamic characteristics of the components of the tilt-roto aircraft.The simulation model was built in MATLAB environment,and the corridor curve in transition mode was obtained by trim calculation.Finally,the cascade PID controllers for attitude Angle and position in quadrotor and fixed wing modes are designed.In order to improve the anti-interference ability of the quadrotor mode,the integral term of tracking error is introduced in the traditional backstepping controller.For dynamic coupling characteristics of transition mode,a constant height transition strategy is proposed,and the gain scheduling conditions are designed to realize the controller switching.The simulation results show that the controllers in the three flight modes meet the basic control requirements.Compared with the cascade PID controller,the anti-interference capability of the integral backstepping controller is increased by 100%.The flight test of the experimental prototype indicate that the height steady-state error of the tilt-rotor aircraft is about 0.2m,the transition time is 8.6s,and the airspeed is 17m/s when switching to the fixed-wing mode.The flight results show that the tilt-rotor UAV designed in this paper meets the design requirements in terms of structure and control system,which provides valuable reference for further research and engineering application in the future.