Trajectory Optimization And Control Of Perching Maneuvers For Aircraft

The study of the aircraft perching maneuvers is inspired by the habitat flying process of birds in nature.Aircraft perching maneuvers can be considered as post-stall landing maneuvers that involves high angle-of-attack(AOA)aerodynamics to produce high drag and rapid deceleration with precise landing.As the manner is out of runway or large recycling space for unmanned aerial vehicle(UAV),utilizing perching maneuvers is infeasible for rest at the terrain's high points to continue execute the task without consuming energy.Perching maneuvers has to go through the post-stall phase,so aerodynamic characteristics can be very complex and greatly affect aircraft's flight characteristics.In this paper,a glider is designed to establish the aerodynamic model directly from free-flight data of real system trajectories.Trajectory optimization and control problems are the focus for perching maneuvers on the longitudinal motion.First of all,aerodynamic model of perching maneuvers is constructed.Based on the flight data,the aerodynamic model of the glider is extracted,and the aerodynamic model is identified by referring to the aerodynamic theory.Finally,a dynamic model is built based on the aerodynamic model.Next,the trajectory optimization problem of aircraft perching maneuvers is studied.Nominal trajectory of perching maneuvers is designed using GPOPS optimization toolbox.Formulations of the perching trajectories in different optimization indexes and initial flight velocity are also compared.Then,the flight states tracking control problem of aircraft perching maneuvers is studied.In order to solve the problem of landing point control,a controller with proportional guidance and PI is designed,and the robustness of the control system is tested.The simulation results show that PI-?control law has better tracking effect than PI-? control law,but the robustness of the two control methods is poor.To improve the control performance,the piecewise linear time-varying optimal control law is designed by using the piecewise-linear system to approximate the original system,and the theoretical proof and simulation analysis are also carried out.At last,the experimental platform of the indoor flight is established.Also the hardware and software architecture of the perching system with the closed-loop controller based on pitch attitude feedback are designed.The results show that the closed-loop control is more accurate than the open-loop control,which demonstrates the feasibility of the perching maneuvers control system.