Constrained Flight Optimal Path Planning For A Avertical Take Off And Landing Fixed Wing Aircraft

In this paper,a new type of vertical take-off and landing fixed wing aircraft is taken as the research object,and the research content is the unmanned aerial vehicle(UAV)flight path planning in the vertical direction.The new type of vertical take-off and landing fixed wing aircraft has the characteristics of helicopter's vertical take-off,vertical landing,hovering abilities,and high altitude horizontal flight of fixed wing aircraft.First of all,the overall structure and layout of the new aircraft are designed,and the geometrical parameters,inertial parameters,aerodynamic parameters and thrust devices,ducted fan motor of the aircraft are determined.On the basis of the optimal control theory,the feasibility of converting the trajectory planning problem into the optimal control problem of a single objective function is discussed.Then the direct algorithm Legendre pseudospectral method for solving the optimal control problem is introduced.The continuous optimal control problem is interpolated into a nonlinear programming problem.Finally,the Tomlab optimization tool is used to solve the trajectory planning problem.The influence of gravity,thrust and thrust torque,aerodynamic force and moment,and aerodynamic force and moment acting on the rudder on the flight motion are fully considered in the mathematical modeling stage.According to the implicated motion,the equations of motion and attitude motion of the UAV are obtained,and then the matrix expression of the six degree of freedom motion equation of the UAV is solved.The overall flight reference path planning for aircraft is designed,and the flight process is divided into four stages: take-off climb section,flat flight section,slide backward pull hovering section and vertical descent section at the end.The objective function with the best energy or the best distance is established.Under the condition of state constraint,initial and final value constraints and control constraints,the motion equations of longitudinal movement of the aircraft are taken as the control objects.By using the Legendre pseudospectral method,the nonlinear state equation is transformed into a linear equation for processing,and the optimal flight track of the aircraft is solved in the MATLAB environment.The simulation results show that the Legnedre pseudospectral method can successfully solve the optimal trajectory planning problem for constrained flight.And the solution process takes a short time and has high precision.The simulation results verify the speediness and reliability of the algorithm.