Design Of Flight Controller For A Tail-sitter UAV

Tail-Sitter UAVs with the advantages of traditional rotorcrafts and fixed wingUAVs are a kind of emerging flying machines. The ability of vertical take-off andlanding enable them to be deployed in the limited environment such as mountainoushilly terrain and narrow city streets. In addition, they also have a high-speed cruisecapability extending the flying time and range. As a result, they have gained muchattention at home and abroad.This article thesis presents a framework of control system design for tail-sitterUAVs. The flight mode is divided into the level-flight mode, the vertical-flightmode and mode. Considering the level-flight mode is similar to fixed wing UAVs,this thesis only researches the control design for the other two flight modes. To dothis, the model for Tail-Sitter UAV is described and analyses. Since the nonlinearand coupling result in difficulty for the controller design, this thesis introduce a newmethod to simplify the model. For the large Angle manetwer, uncertain descriptionand parameter perturbation, This article utilizes theL1adaption control theory tofulfill the control system design.Firstly, in this paper we eatablish the mathematical mode for tail-sitter UAV，which based on vertical Euler Angle and horizontal Euler Angle. This not onlyavoids the singularity in the vertical flight mode, but also has a clear physicalmeaning with respect to the terms of the unit quaternion. Next through the researchof Tail-Sitter UAV’s aerodynamic layout and configuration, we establish the forcesand moments generated model of gas rudder and air rudder, thereby establish the sixdegrees of freedom nonlinear mathematical models of Tail-Sitter UAV’s.Then, in order to facilitate the design of flight control system, we simplify themathematical model of Tail-Sitter UAV based on the coupling characteristics. So,we linearize the nonlinear model of Tail-Sitter UAV near the trim point, thendecouple the linearization model. We can get four independent control loop: theailerons to roll angle, the elevator to pitch angle, the rudder to yaw angle andthrottle to airspeed.Finally, we utilizes the adaption control theory to fulfill the vertica modeflight controller and system design ransition flight mode controller. The verticalflight mode controller is made up of three attitude control loop and a velocitycontrol loop; the attitude control loop use theL1adaptive controller which using theLQR for expected closed-loop system design, the velocity control loop ues the conventional PI controller. Transition flight mode controller design is based on theoriginal on the basis of vertical and horizontal flight controllers. Numericalsimulations verify the performance of flight controllers, even in the presence ofparameter perturbation and unmodelled dynamic characteristics, it still has a goodtransient performance and steady-state performance.