Controller Design For Fixed-wing UAV's Guided System

Fixed wing UAV is widely used in military and civil fields because of its unique advantages. High performance flight control system of UAV is the key to complete the complex tasks. The guidance and control system is one of the core subsystems of flight control system, and it is the key to realize the trajectory tracking and target tracking. Therefore, it is meaningful to study the control and guidance technology for UAV.At present, the problems for guidance and control design are divided into a problem of outer-loop guidance and a problem pf inner-loop control design. The main research work is to design the controllers of guidance and attitude. The attitude controller design is mainly based on the PID control algorithm, and the guidance controller design is based on the sliding mode control algorithm. The main research contents are as follows:Firstly, this paper introduces two kinds of guidance and control system design schemes and decides the scheme adopted in this paper. The research status of UAV attitude control and guidance technology is preseneted, and the principle of PID and sliding mode control is analyzed in details.Then, this paper compares the characteristic of UAV's different turning modes, the kinematics property of the UAV turning motio is analyzed in different turning modes, and the control law of the roll and pitch channel is also deduced. The feedback of inner loop angular rate is introduced to solve the oscillation problem. In order to introduce angular rate feedback, the angle control is converted into the control of angular velocity. Based on the PID control algorithm and the aerodynamic characteristics of UAV, the attitude controller of roll and pitch channels design are completed.Finally, the UAV guidance algorithm is explored by using sliding mode control. This paper introduces the definition of straight-line paths and lotier following. According to the ideal correction motion of cross track error, the sliding surface is designed and its stability is proved. The guidance control law is derived by the designed sliding surface and the motion state equation of the system. To solve the chattering problem of the designed control law, a continuous control is adopted to replace the switch control. The stablity of the proposed control law is proved using Lyapunov theory.The flight test results show that the accuracy of designed attitude controller is about two degree. The designed attitude controller has the merits of fast response and small overshoot. The chattering of the designed guidance controller is effectively reduced, and the control precision is about three meters.